percpu: add percpu_counter_add_local and percpu_counter_sub_local

Patch series "/msg: mitigate the lock contention in ipc/msg", v6.

Here are two patches to mitigate the lock contention in ipc/msg.

The 1st patch is to add the new interface percpu_counter_add_local and
percpu_counter_sub_local.  The batch size in percpu_counter_add_batch
should be very large in heavy writing and rare reading case.  Add the
"_local" version, and mostly it will do local adding, reduce the global
updating and mitigate lock contention in writing.

The 2nd patch is to use percpu_counter instead of atomic update in
ipc/msg.  The msg_bytes and msg_hdrs atomic counters are frequently
updated when IPC msg queue is in heavy use, causing heavy cache bounce and
overhead.  Change them to percpu_counter greatly improve the performance. 
Since there is one percpu struct per namespace, additional memory cost is
minimal.  Reading of the count done in msgctl call, which is infrequent. 
So the need to sum up the counts in each CPU is infrequent.


This patch (of 2):

The batch size in percpu_counter_add_batch should be very large in
heavy writing and rare reading case. Add the "_local" version, and
mostly it will do local adding, reduce the global updating and
mitigate lock contention in writing.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jiebin Sun <[email protected]>
Reviewed-by: Tim Chen <[email protected]>
Cc: Alexander Mikhalitsyn <[email protected]>
Cc: Alexey Gladkov <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: "Eric W . Biederman" <[email protected]>
Cc: Manfred Spraul <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Vasily Averin <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions